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 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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 */
package java.util;

import java.util.function.IntConsumer;
import java.util.stream.Collector;

/**
 * A state object for collecting statistics such as count, min, max, sum, and
 * average.
 *
 * <p>This class is designed to work with (though does not require)
 * {@linkplain java.util.stream streams}. For example, you can compute
 * summary statistics on a stream of ints with:
 * <pre> {@code
 * IntSummaryStatistics stats = intStream.collect(IntSummaryStatistics::new,
 *                                                IntSummaryStatistics::accept,
 *                                                IntSummaryStatistics::combine);
 * }</pre>
 *
 * <p>{@code IntSummaryStatistics} can be used as a
 * {@linkplain java.util.stream.Stream#collect(Collector) reduction}
 * target for a {@linkplain java.util.stream.Stream stream}. For example:
 *
 * <pre> {@code
 * IntSummaryStatistics stats = people.stream()
 *                                    .collect(Collectors.summarizingInt(Person::getDependents));
 * }</pre>
 *
 * This computes, in a single pass, the count of people, as well as the minimum,
 * maximum, sum, and average of their number of dependents.
 *
 * @implNote This implementation is not thread safe. However, it is safe to use {@link
 * java.util.stream.Collectors#summarizingInt(java.util.function.ToIntFunction)
 * Collectors.toIntStatistics()} on a parallel stream, because the parallel implementation of {@link
 * java.util.stream.Stream#collect Stream.collect()} provides the necessary partitioning, isolation,
 * and merging of results for safe and efficient parallel execution.
 *
 * <p>This implementation does not check for overflow of the sum.
 * @since 1.8
 */
public class IntSummaryStatistics implements IntConsumer {

  private long count;
  private long sum;
  private int min = Integer.MAX_VALUE;
  private int max = Integer.MIN_VALUE;

  /**
   * Construct an empty instance with zero count, zero sum,
   * {@code Integer.MAX_VALUE} min, {@code Integer.MIN_VALUE} max and zero
   * average.
   */
  public IntSummaryStatistics() {
  }

  /**
   * Records a new value into the summary information
   *
   * @param value the input value
   */
  @Override
  public void accept(int value) {
    ++count;
    sum += value;
    min = Math.min(min, value);
    max = Math.max(max, value);
  }

  /**
   * Combines the state of another {@code IntSummaryStatistics} into this one.
   *
   * @param other another {@code IntSummaryStatistics}
   * @throws NullPointerException if {@code other} is null
   */
  public void combine(IntSummaryStatistics other) {
    count += other.count;
    sum += other.sum;
    min = Math.min(min, other.min);
    max = Math.max(max, other.max);
  }

  /**
   * Returns the count of values recorded.
   *
   * @return the count of values
   */
  public final long getCount() {
    return count;
  }

  /**
   * Returns the sum of values recorded, or zero if no values have been
   * recorded.
   *
   * @return the sum of values, or zero if none
   */
  public final long getSum() {
    return sum;
  }

  /**
   * Returns the minimum value recorded, or {@code Integer.MAX_VALUE} if no
   * values have been recorded.
   *
   * @return the minimum value, or {@code Integer.MAX_VALUE} if none
   */
  public final int getMin() {
    return min;
  }

  /**
   * Returns the maximum value recorded, or {@code Integer.MIN_VALUE} if no
   * values have been recorded.
   *
   * @return the maximum value, or {@code Integer.MIN_VALUE} if none
   */
  public final int getMax() {
    return max;
  }

  /**
   * Returns the arithmetic mean of values recorded, or zero if no values have been
   * recorded.
   *
   * @return the arithmetic mean of values, or zero if none
   */
  public final double getAverage() {
    return getCount() > 0 ? (double) getSum() / getCount() : 0.0d;
  }

  @Override
  /**
   * {@inheritDoc}
   *
   * Returns a non-empty string representation of this object suitable for
   * debugging. The exact presentation format is unspecified and may vary
   * between implementations and versions.
   */
  public String toString() {
    return String.format(
        "%s{count=%d, sum=%d, min=%d, average=%f, max=%d}",
        this.getClass().getSimpleName(),
        getCount(),
        getSum(),
        getMin(),
        getAverage(),
        getMax());
  }
}
